This invention relates to a method and an apparatus for generating multi-gradation data to represent characters according to light and shade information.
In a conventional computer system, fonts are used for representing characters. In a conventional computer system, each character in a given font is specified as a small rectangular bitmap, a ones and zeros representation of the rectangular array of pixels. For example, an alphabet is composed of eight pixels.times.eight pixels. A kanji character is composed of sixteen pixels.times.sixteen pixels. A raster display of the computer system stores the display primitives such as lines and characters in a refresh buffer in terms of their component pixels. The complete image on the raster display is formed from the raster, which is a set of horizontal raster lines, each a row of individual pixels. The raster is thus stored as a matrix of pixels representing the entire screen area. The entire image is scanned out by a video controller, allowing the constant refresh of the display. As known in the arts, there are two fundamental types of refresh: interlaced and noninterlaced. The former is used in broadcast television and in raster display designed to drive regular television. The refresh cycle is broken into two fields, each lasting 1/60 second; thus, a full refresh lasts 1/30 second. All odd-numbered scan lines are displayed in the first field, and all even-numbered ones are displayed in the second. The purpose of the interlaced scan is to place some new information in all areas of the screen at a 60-Hz rate, since a 30-Hz refresh rate tends to cause flicker. On the other hand, noninterlaced scan is used to scanout one raster line at a time from top to bottom. In other words, scanout starts in the upper left-hand corner of the display and simultaneously moves left to right and top to bottom to put a series of zig-zag lines on the screen.
Some television sets for home use include a device applying an interlaced scan technique. In this event, flicker appears on the screen. Accordingly, if small characters are displayed on the screen, flicker hinders clear recognition of the characters.